Piercing point



Patented Mar. 13, 1934 PIERCIN G POINT Edwin 0. Wright and Ellwood City, Pa., assi 'Donald N. Uebelhart,

more to National Tube Company,- a corporation of New Jersey Application February 23, 1932, Serial No. 594,729

This invention relates to piercing points used in the manufacture of seamless tubing, and has for its object the provision of a novel form of piercing point adapted to be water-cooled while. in use. 4

,Since the early stages of the development of the seamless tube art the mills have used a. tubular bar to hold the piercer point in the piercing mill while piercing the solid billet from 1 which the tube is formed. The tubular blank or shell formed from the billet fits over the point onto the piercer bar or mandrel, heatin the bar or mandrel to a high temperature, especially on the rapid working of the mills in use at the present time. The piercer bar or mandrel must, therefore, be cooled internally by water to mainta'n its strength and to prevent frequent mill shut-downsto change bars. The end of the bar nearest the piercer is closed 20 with, a solid forging or casting known as the bar plug or cap, which plug or cap is threaded into the end of the bar and serves to support the piercer point. o A

The piercer point heretofore in general use has been a solid steel casting or forging which is mounted on the bar or caps During the piercingoperation this solid piercing point gets excessively hot and must be removed after each billet has been pierced, and a fresh point pressed on the bar plug to start the next billet. The heated solid points are cooled in a water bosh before being used again, and generally may be used for piercing from twenty-five to fifty billets before being scrapped. Frequently, when piercing long lengths or very light walled tubing, the service obtained from the solid point is very poor and results in the production of a high percentage of defective pipe.

Attempts have been made to overcome the objections to the solid piercing points of the prior art by the use, of special alloys endpoints formed of a combination of metals, However, such attempts have failed to materially improve the piercing points. i5 Experience has shown the art, however, that the. main objections-to the prior art points have ted from the inability to dissipate heat from the piercing points. The present invention,

therefore, provides a hollow water-cooled piercing point which will remain sufllciently c001,.

during the piercing on successive piercing ing heated to such a will be affected.

In order that a wa operation, for continuous use operations without becomdecree that its usefulness r-cooled piercer point leakage ofwater is also that the bar plug or cap metal may be successful in operation it is necessary that the mandrel or piercer bar, the bar plug cap and the piercer points allbe water-tight and rigidly held together. It is also necessary that the parts be so des'gned and constructed that they will withstand the extreme forces to which they will be subjected during the piercing operations. The piercer point construction of this application is adapted to answer all the requirements set forth above.

Inthe drawing:

F.gure l is a sectionalplan through a piercing point constructed in accordance with this invention.

Figures 2 and 3 are sectional elevations taken on the lines 11-11 and IIL-III of Figure 1.

Referring more particularly to the drawing, the numeral 1 designatesthe mandrel or piercer bar which isof tubular construction and has a threaded connection with one end .of a hollow bar plug or cap 2, which may be formed of a steel casting or forging. The piercer point is designated generally by the numeral 10 and is of hollow construction. The point may also be formed from a suita le steel forging'or' casting.

The bar or plug 2 is provided with a tapered end or nose which is machined and ground to a smooth finish and fitted within the rear end of the piercer point 10. The interior surface of the point 10 is tapered inwardly from the rear end of the point toward the nose end for a length equal to the tapered end 2' of the bar plug 2 forming a sleeve portion 5. The sleeve portion 5 .is provided with a .machined and ground finish so as to make a tight driving lit with the ground surface of the end 2' of the plug 2. The interior of the point forward of the sleeve portion 5 is providedwith a plurality of annular flutes forming annular fins. or ribs 6 which serve the dual purpose of strengthening the. point and also provide an increased surface for dissipating the heat from the point. The side walls of the point intermediate the fins 6 are of reduced thickness. The thin wall sections between the ribs or fins 6 are made possible due to the supporting or strengthening ac-' tion of the ribs or fins, and such thin sections aid materially in maintaining the point cool during the piercing operations.

The end pressure on the piercer point during the'pierclng operation serves to tighten the connection or joint between the point 10 and the end 2" of the plug 2 and effectively prevent the from the point assembly. It

and piercer point metal have the same coeflicient of expansion in order that the joint between the cap or plug 2 and'the point 1 may stay tight during the use of the piercer point. The plug or cap 2 is bored longitudinally to provide a water passage from the bar 1 into the point 10, and a water-circulating pipe 3 projects through the bar 1 and plug 2 into the point to a location adjacent the nose end of the point. The pipe 3 is of less diameter than the bore 4 in the plug or cap 2 so as to provide an opening in the cap or plug 2 surrounding the pipe 3 having an area at least equal to that of the bore of the pipe 3.

Theincoming water passes through the pipe 3, impinges upon and washes the whole inside surface of the point, bar cap or plug and bar, cooling all three units in an effective manner. Due to the fact that the space around the pipe 3 in the cap 2 and bar 1 is at least equal in cross-sectional area to the cross-sectional area of the bore in the pipe 3, a free and uniform flow of water through the assembly takes place. Therefore, a sufflcient water pressure is not built 'up to disrupt the connection between the point 10 and the plug or cap 2.

The wall thickness of the piercer point must be carefully regulated to give the requisite strength, and also be as thin as possible for rapid cooling. For small points between two inches and five inches outside diameter, the best wall thickness, so far as present experience has shown, should be approximately one-eighth of the outside diameter of the point, and for points I ranging from five inches to eight inches outside diameter a wall thickness of-three-fourths of an inch has proved most satisfactory.

While we have shown and described one specific form of our invention, it will be understood that we do not wish to be limited thereto since various modifications may be made without departing from the scope of our invention, as defined in the appended claims.

We claim:

1. A piercing point adapted for water cooling comprising, in combination, a. bar plug portion having a bore extending longitudinally therethrough, a tapered end projecting from said' plug and having a ground finish, and a hollow point having a tapered and ground finished sleeve portion extending inwardly from its rear end a distance substantially equal 'to the length of said tapered end portion of said bar plug and adapted to receive said tapered end of said plug, and a plurality of annular fins projecting from the interior surface of said point, the side walls of said point intermediate said fins being materially thinner than the other portions of said point.

' 2. A piercing point adapted for water-cooling comprising, in combination, a bar plug portion having a bore extending longitudinally therethrough, a tapered end projecting from said plug and having a ground finish, a hollow point having a tapered and ground finished sleeve portion extending rearwardly from its rear end for a length substantially equal to the length of said tapered end portion of said bar plug and adapted to receive said tapered end of said plug, said point having a driving fit in said plug, a plurality of annular fins projecting from the interior surface of said point, said point and said bar plug being composed of metal having the same coeflicient of expansion, and a watercirculating pipe extending through the bore in said plug and terminating short of the nose end 'of said point, the bore of said bar plug being of such size that the space around said watercirculating pipe will have a cross-sectional area at least equal to the cross-sectional area of the bore of said pipe. I

3. A piercing point adapted for water cooling comprising, in combination, a bar plug portion having a bore extending longitudinally therethrough, a tapered end projecting from said plug and having a ground finish, and a hollow point having a tapered and ground finished sleeve portion extending inwardly from its rear end a distance substantially equal to the length of said tapered end portion of said bar plug and adapted to receive said tapered end of said plug, and a' plurality of fins projecting from the interior surface of said point, the side walls of said point intermediate said fins being materially thinner than the other portions of said point.

EDWIN C. WRIGHT. DONALD N. UEBELHART. 

